'Sand battery' could solve green energy's big problem

Fascinating stuff. Some numbers from the startup website[1]:

- - The storage has 100 kW heating power and 8 MWh capacity.

- three times superior to water-based storage and beyond boiling point [2]

- related scientific work, using granite [3]

[1] https://polarnightenergy.fi/technology

[2] https://www.youtube.com/watch?v=tm7spMG0ch8&t=871s

[3] https://www.mdpi.com/1996-1073/13/21/5662/pdf